Device alias returning UTF-16 encoded string

[road-cycling]

Problem devices are returning byte strings containing UTF-16 characters when queried for their alias/description.

Updating the plugin_polling_device_interface_metrics.py file with the following changes will cause python to ignore the problem characters.

        return self.enrichment.get_enrichment_value(u'self', u'interface', interface_index) \
                              .get(u'alias') \
                              .encode(u'ascii', u'ignore')

    def get_description(self, interface_index):
        return self.enrichment.get_enrichment_value(u'self', u'interface', interface_index) \
                              .get(u'description') \
                              .encode(u'ascii', u'ignore')